Birth is a major turning point in the life of the newborn, as it moves from intrauterine life to extrauterine life. This sudden transition forces the newborn to adapt quickly. Oxygenation, which was only provided by the placenta during uterine life, will have to be provided by the lungs, which will open when the newborn cries for the first time. This phenomenon will change the way blood reaches the lungs and will require the newborn's heart to work harder. In addition, the cardiac workload will also increase due to the clamping of the umbilical cord, which will force the heart to pump through more resistant blood vessels.

This transition, generally well tolerated in newborns at term, can be much more complicated in premature newborns, particularly in extremely low gestational age newborns (e.g. ELGAN, born before 28 weeks of amenorrhoea). There are several causes of this difficult adaptation on the cardiovascular system: poor heart function, difficulty in revascularizing lungs due to the physiological characteristics of premature newborns (high pulmonary vascular resistance, persistence of the ductus arteriosus), and a tone of the blood vessel muscles that is probably immature. In addition, respiratory failure is often associated with pulmonary immaturity.

The consequences of a difficult adaptation to extrauterine life, combined with cardiovascular failure, will be poor organ perfusion, whose brain. Moreover, ELGANs have immature regulation of their brain vascularisation. Variations in the vascularisation of the brain (in the event of cardiovascular failure) may be responsible for irreversible lesions with intraventricular hemorrhage. Ultimately, these bleedings carry a high risk of mortality or severe disability in premature infants.

Several hypotheses have been put forward as to the causes of this poor adaptation to extrauterine life, but there are few recommendations on adapted medical management. Cardiac ultrasound and the use of drugs to support the heart and blood vessels have been suggested. However, a large number of ELGANs will develop complications that investigators cannot predict or intervene in time. In addition, studies on the drugs used have not been carried out on ELGANs, which limits the conclusions investigators can draw.

These factors encourage us to improve our fundamental knowledge of the cardiovascular system in the ELGANs. The aim is to identify the most effective clinical tools and treatments for assessing and treating neonatal cardiovascular failure at an early stage, before complications appear. Investigators aim to compare the architecture and composition of the heart, blood vessels, and blood of fetuses under 28 weeks of amenorrhea gestation with those of fetuses over or equal to 34 weeks of amenorrhea gestation.

For this research, investigators need tissues (heart muscle, blood, and vessels) from fetuses of different ages. These tissues are usually already taken during the foetopathology examination to try to provide a medical explanation of the medical abortion. There will be no change to the foetopathology examination carried out on the foetus, with the exception that some of the tissue taken will have additional analyses carried out in our INSERM laboratory attached to the Montpellier University Hospital.

Population resulting from medical abortion is motivated by the ethical impossibility of taking such invasive samples from live newborns. The non-use of animals is justified by the difficulty of extrapolating results to humans. The indication for abortion and its performance will be carried out by current practice. Participants will be offered and explained the study during the pre abortion visit.

This research does not alter the patient's care. No additional examination or consultation is required. No personal benefit is expected from the study, but it will enable us to gain a better understanding of ELGAN's hemodynamics and to consider future clinical studies.

Inclusion Criteria:

For the pregnant women:

• Over 18 years old.
• Speaks and understands French.
• Medical abortion requested by the participant, scheduled and validated by the CPDPN of the Montpellier University Hospital.
• Participant's agreement to use for research purposes the biological tissues from the systematic foetopathological examination.

For fetuses:

• Interest group: Fœtus ≥ 22 WA and <28 WA
• Control group: Fœtus ≥ 34 WA

Exclusion Criteria:

For the pregnant women :

• Injection of betamethasone or maternal use of dexamethasone in the month before foeticide
• Known family genetic mutation that may be linked with cardiomyopathy
• Failure to obtain consent (adults, unemancipated minors, persons unable to give consent)
• Not affiliated to a social security
• Persons under legal protection
• Person taking part in another research study with an exclusion period still in progress.

For fetuses:

• Fetus from unplanned in-utero death
• Significant cardiac malformation suspected antenatally (excluding atrial septal defect ostium secundum and isolated muscular ventricular septal defect).
• Suspected abnormality of myocardial tissue
• Biological tissue sampling more than 48 hours after fœticide

All pregnant woman who will receive a medical abortion at Montpellier Hospital and who present eligibility criteria for her and her foetus will be invited to participate to the study

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.